Elmer A. Sperry_Father of modern navigation technology.

                         The First Question comes in our mind :

1 :Who was Elmer Ambrose Sperry? 
  2 :What was the Gyroscopic Compass?

  
Elmer Ambrose Sperry Sr. (October 12, 1860 – June 16, 1930) was an American inventor , and Father of modern navigation technology.
In the year 1913, Sperry created a gyro that could control the elevators and ailerons of an aircraft through a series of servos.
2 :What was the Gyroscopic Compass:  A Gyroscope (from the Greek ‘gyro’ means turn or revolution and ‘skopein’, means to view) is an apparatus in which a heavy flywheel or top rotates at high speed, the turning movement resisting change of direction of axis. 
There are 4 laws or facts act upon which gyrocompass operation depends, the first two are internal properties of the gyroscope namely.
1:Gyroscopic inertia (rigidly in space)
2:Precession
 3: Earth  rotation 
 4:Earth’s  and gravitation.
There is nothing mysterious about the gyroscope. Its actions, though they may appear at first to defy the laws of physics, in reality depend entirely upon Sir Isaac Newton's Laws of Motion.
 Many of the toys we used to play with were based on gyroscopic principles. A spinning top is an elementary form of gyroscope, the "diabolo" -- once a popular object for pastime -- is another; so also is a hoop, for it will exhibit the characteristics of a gyro as long as it has sufficient motion to roll along the ground.

All of the practical applications of the gyroscope are based upon two fundamental characteristics, namely: "Gyroscopic Inertia" and "Precession".
Gyroscopic properties are inherent in all rotating masses, but can best be observed in those which have the greatest amount of freedom about two axes in addition to the spinning axis. 
The top comes under the latter category. The engine flywheel, on the other hand, is limited to one angular axis of freedom -- its spinning axis.
 A rifle bullet may be likened to a gyroscope because it is free to revolve about two other axes, in addition to its spinning axis; therefore it exhibits gyroscopic inertia, tending to maintain a straighter line of flight than it would if not rotating.
 A windmill has freedom about its spinning axis and also about a vertical axis (as it must be able to turn in any direction under the control of its rudder). However, it has no freedom about a horizontal axis other than its spinning axis, and therefore, although precessional forces are impressed upon the apparatus by shifts of wind, there are no visible effects. 
The precessional forces result in a torque which is absorbed in the bearings. In a windmill these forces are small, however, owing to the light construction of the fan. In order to obtain maximum gyroscopic effects a rotor should be comparatively heavy, with as much of its weight concentrated at the rim as practicable, and it should spin with considerable velocity.

 Gyroscopic inertia depends upon angular velocity, weight and radius at which the weight is concentrated. Maximum effect is obtained therefore from a mass, with its principal weight concentrated near the rim, rotating at high speed.